1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile machine.
2. Description of the Related Art
In recent electrophotographic image forming apparatuses, toner used as developing agent scatters, and dust sometimes floats, depending on the use environment. Since an optical unit provided in the image forming apparatuses is sensitive to toner and dust, the interior of the optical unit is hermetically sealed so as to prevent the entry of toner and dust. Further, an aperture is provided so that laser light emitted from the optical unit passes therethrough. In order to prevent toner and dust from entering the optical unit, a cover glass that transmits the laser light is provided at the aperture.
In this configuration, a decrease in printing density and an image deficit are sometimes caused when toner and dust dropping from the developing section and floating in the image forming apparatus enter the optical path of exposure light, adhere to the cover glass, and block the optical path. In order to avoid the decrease in density and the image deficit described above, it is necessary to devise a structure that prevents toner and dust from adhering to the cover glass.
Hitherto, a user or serviceman has accessed the interior of the image forming apparatus and has cleaned the cover glass with a soft cloth or the like. However, since the area of the aperture having the cover glass is small and cleaning needs to be performed without scratching the surface of the cover glass, the cleaning operation is considerably troublesome, and sufficient cleaning is difficult.
In order to overcome these problems, various cleaning structures for removing toner and dust from the cover glass have been proposed. For example, Japanese Patent Laid-Open No. 4-159574 discloses a cleaning device that allows the user or serviceman to remove toner and dust from a cover glass simply by sliding a cleaning member formed of synthetic resin foam via a support means provided in an optical unit.
Japanese Patent Laid-Open No. 2005-313459 (corresponding to US Patent Publ. No. 2005/243156) discloses a cleaning structure in which a shutter member for closing and opening the optical path of a light beam is provided with a seal member, and the seal member includes a cleaning member that slides on the cover glass.
Japanese Patent Laid-Open No. 63-75764 discloses a cleaning mechanism in which a shutter includes a plurality of cleaners each formed by an elastic blade, a brush, or a fleece cloth, and the cleaners slide on a light emitting window of an optical device.
Japanese Patent Laid-Open No. 2004-333799 discloses that a scanner cover includes a plurality of cleaners each formed by a brush or an elastic member and the cleaners clean a dustproof glass of a laser scanner while being in contact with the dustproof glass.
In recent years, the environment in which the image forming apparatus is installed has been diversified, and various substances adhere to the cover glass. Specifically, the substances include not only toner, but also dust in the air and wear powder produced in the body of the image forming apparatus. Since the substances vary in particle size and shapes, even when cleaning is performed by moving toner and dust with an elastic blade or a brush serving as a cleaning member, it is difficult to completely remove toner and dust having a minute particle size and shape. This may result in an image defect.
The amount of toner and dust adhering to the cover glass tends to increase as the life of the image forming apparatus increases. For this reason, there is an increasing fear that a lot of toner and dust adhering to the cover glass will not be completely wiped away by cloth or sponge serving as a cleaning member and that this may cause an image defect. That is, since the cleaning performance of the wiping cleaning member easily saturates, it is necessary to replace the cleaning member many times in the life of the apparatus. Moreover, the wiped toner and dust may adhere from the cleaning member onto the cover glass again.
In addition, with size reduction and increases in output speed of the image forming apparatus, the amount of heat generated in the image forming apparatus has increased, and the necessity of cooling the interior of the image forming apparatus has been raised in order to ensure a high image print quality. Practically, external air is taken into the image forming apparatus and is blown on a heat generating portion, thus cooling the interior of the image forming apparatus. For this reason, the amount of dust entering the image forming apparatus increases, and toner scatters in a wider area in the image forming apparatus. Consequently, the possibility that toner and dust will adhere to the cover glass increases.